Cam controlled cutting apparatus

ABSTRACT

A cutting apparatus for cutting the surface of a workpiece along intersecting paths and including a cam-cam follower mechanism, cutting means mounted on the follower part of the mechanism, driving means for moving the cam and follower relative to each other to move the cutting means successively along said paths, and control means associated with the cam-cam follower mechanism for turning the follower on the cam to move the cutting means from one path to the other while holding the cutting means at the intersection of the two paths.

nited States Patent [1 1 Hoglund CAM CONTROLLED CUTTING APPARATUSinventor: Nils 0. Hoglund, Shorti-mlswjf Assignee: Tri-OrdinateCorporation,

Bakers HeightsfN J'.

Filed; Nov. 24,1571 0 Appl. No.: 201,776

,us. Cl 90/245, 82/19, 90/30, 7

Int. Cl. B23d l/30, 823d 5/04 Field of Search 90/243, 30, 31', 82/12,1.3, 1.4, 1.5, 19

References Cited UNITED STATES PATENTS 5/1886 Helbling ..90/24.3 7/1906Waldron 82/13 Primary Examiner-Francis S. Husar Attorney-Dean S.Edmonds, Harry C. Jones et al,

[51] ABSTRACT A cutting apparatus for cutting the surface ofa workpiecealong intersecting paths and including a cam-cam follower mechanism,cutting means mounted on the follower part of the mechanism, drivingmeans for moving the cam and follower relative to each other to move thecutting means successively along said paths, and control meansassociated with the cam-cam follower mechanism for turning the followeron the cam to move the cutting means from one path to the other whileholding the cutting means at the intersection of the two paths.

25 Claims, 26 Drawing Figures Patented Aug. 14, 1973 13 Sheets-Sheet 1 rd n u R W 0 E T N m V 1 N n N Y B Patented Aug. 14, 1973 3,752,037

13 ShootsShuut 2 P INVENTOR Nil O.Ho lund M2041, 3/.

ATTORNEYS Patented Aug. 14, 1973 3,752,037

13 Sheets-Sheet :5

Patented Aug. 14, 1973 3,752,037

13 Sheets-Sheet 4 INVENTOR Nil 0. Hoglund m, ba /x11;

TTORNEYS Patented Aug. 14, 1973 3,752,037

13 Sheets-Sheet 5 FIG. 7

ullmn HHHH 39 !NVENTOR ws O.Hogl n BY M, fi\ )y w ATTORNEYS PatentedAug. 14, 1973 3,752,037

13 Sheets-Sheet lNVENTOR ATTORNEYS Patented Aug. 14, 1973 15S110cts-5hcet 2' INVENTOR sQHo lund fi m ATTORNEYS BYE} m,

Patented Aug. 14, 1973 13 Sheets-Sheet INVENTOR ATTORNEYS 4 9 En 1 i u mM n M 2 9 v, 6 4 9 wu igz 4 9 13 Sheets-Sheet 11 FIG.12

INVENTOR Nils. O. Hoglund M,am'

ATTORNEYS Patented Aug. 14, 1973 3,752,037

15 Sheets-Sheet 10 FIG. 14

FIG. 15 FIG.16

INVENTOR Nils O .Hoglund BY W1;- m, q zm' ATTORNEYS Patented Aug. 14,1973 3,752,037

13 Sheets-Sheet 11.

FIG. 21

INVENTOR fi ls Q.Hoglznd E117 {ZIATTORNEYS Patented Aug. 14, 19733,752,037

13 Sheets-Sheet L2 lNVENTOR Nils Hoglund BYKKMZ ATTORNEYS Patented Aug.14, 1973 3,752,037

13 Sheets-Sheet l5 INVENTOR Nils O. Hoglund BY/ M r M, 5

ATTORNEYS CAM CONTROLLED CUTTING APPARATUS BACKGROUND OF THE INVENTIONRecently, the Wankel engine has become of great interest as a possiblesubstitute for the conventional reciprocating piston engine. This hasbeen brought about mainly by the public concern over pollution of theatmosphere as caused by the piston engine.

In construction, the Wankel engine includes a stator housing having arotor rotating within a bore formed in the housing. The shape of thehousing bore is epitrochoidal and the rotor is mounted eccentrically ona shaft rotating centrally within the bore. In shape, the rotor isgenerally triangular with the sides having a slight convex curvature. Inorder to provide for the induction, compression, ignition and exhaust ofthe gas fuel as the rotor'rotates within the bore, it is necessary thatthe rotor be provided with seals cooperating with the stator to formseparate chambers. Sealing is necessary at the three apexes of the rotorwhere contact with the wall surface of the bore is made andalong theopposite side faces of the rotor for sealing the rotor against the endwalls of the housing bore.

The seals on the side faces of the rotor as well as those at the apexesmust be precisely oriented so as to maintain a proper sealing with thestator. With present constructions, the seals are attached to the rotorby seating within seal grooves formed in the rotor. With respect to thegrooves in the sides of the rotor, they extend in arcuate paths adjacentthe three edges of the rotor, a pair of grooves being providedadjacenteach edge for a total of six grooves on each side of the rotor.

In order to properly hold the seals within the grooves they must beaccurately formed to a uniform depth and width throughout their length.If this is not done, the seals will tend to fall out of the grooves ormake uneven contact with the end walls of the stator housing. Theformation of the grooves in the sides of the rotor is furthercomplicated by the fact that these grooves must intersect each other atthe apexes of the rotor without extending to the edge of the rotor. Thischaracteristic of the grooves makes it necessary that the cutting of anyone groove must be stopped before it reaches an apex of the rotor andthe cutting means moved out of this groove and into alignment forcutting the adjacent groove running to the next apex of the rotor. v

The cutting of the grooves in the rotor could be made more efficient ifthey could extend to the edges of the rotor and it was not required thatthey turn within the small zones adjacent the apexes. With the closedpath formed by the seal grooves, however, the cutting operation ofpresently available equipment has been rather time consuming. Also, theaccuracy required in cutting the grooves as well as their shape andorientation on the rotor has made present cutting equipment forperforming this operation inefficient.

With one type of cutting apparatus presently available, the grooves inthe side faces of the rotor are cut by a milling operation. A circularmilling cutter is used for cutting each groove to its final depth andshape in one stroke. In order to do this, however, the milling cuttermust be moved very slowly through the workpiece; and with a total ofthree pairs of grooves on each side of the rotor it takes twelve strokesto complete the cutting operation on both sides of the rotor.

Instead of cutting the grooves to their final configuration in onestroke, attempts have been made to cut the grooves in a series ofsuccessive cuts, each a little deeper than the next. With equipment ofthis nature, a single cutting tool is used and fed through multiplestrokes along each of the paths where the grooves are to be formed. Atthe end of each cutting stroke the cutting tool is raised out of theworkpiece, returned to its starting position and then lowered back ontothe workpiece a few thousandths of an inch deeper than with the lastcutting stroke. It is apparent that with the return stroke performing nocutting operation, the time required to cut the grooves in the rotor israther long.

SUMMARY OF THE INVENTION In accordance with the teachings of the presentinvention, the cutting of the side grooves in the rotor is performedquickly and efficiently. In addition, the grooves are cut with a highdegree of precision so as to securely hold the seals in place and effectproper sealing thereof with the end walls of the stator.

In construction, the cutting apparatus of the present inventiongenerally includes an annular cam member which is positioned inencircling relation with the rotor. Carn follower means are associatedwith the cam member and hold the cutting means of the apparatus. The cammember has cam tracking surfaces which are followed by the followermeans and which correspond to the three paths through which the cuttingmeans must move along the workpiece to cut the pairs of grooves adjacentthe three edges of the rotor. The cam also includes tracking surfaceswhich cause the cutting means to turn within the zones of intersectionof the paths being cut on the workpiece so that the cutters may movefrom one path to the next adjacent path during continuous movement ofthe cam follower means about the cam and without losing any appreciabletime.

In accordance with the teachings of the present invention, the cuttingapparatus includes three separate cutting units mounted on three camfollowers for continuous movement about the rotor workpiece with each ofthe cutting units performing a cutting stroke adjacent one of the edgesof the rotor. With each cutting stroke of the cutting units, the groovesare cut to a fraction of the final depth desired. When the cutters reachthe points of intersection of the grooves, the rotor workpiece andcutters are movedrelative to each other by a small increment so that thenext cutting stroke will be at a greater depth within the rotorworkpiece.

Instead of providing cutters having a cutting edge shaped to the finaldesired groove contour, the cutting apparatus of the presentinvention'includes a pairof differently shaped cutters in each of thethree cutting units. A pair of cutters is required in each cutting unitsince a pair of grooves is to be cut adjacent each edge of the rotor.The cutters of one of the cutting units are constructed for roughcutting the grooves, the cutters of the next unit are used forsemi-finishing and the cutters of the third unit are used for finishingthe grooves to the precise shapeand dimension required for sealing theseals. The cutters of each unit are also constructed so that they assisteach other in providing. both an efficient and precise cutting of thegrooves.

When using the cutting apparatus of the present invention, productioncapacity'and efficiency over conventional equipment will increasemanyfold; and this, in turn, will reduce manufacturing costs. 'As far asthe quality of the finished product is concerned, applicant's inventionpermits the production of grooves having a BRIEF DESCRIPTION OF THEDRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1,the cutting apparatus of the pres- FIG. 1 is a side elevation of oneembodiment of the em invention generally inch-(165 a framework 1 oncutting apparatus of the present invention;

FIG. 2 is a plan view of a workpiece in which grooves have been cut bythe apparatus of FIG. 1;

FIG. 3 is a view showing the orientation of the work- I piece relativeto the cam-cam follower mechanism of the cutting apparatus of thepresent invention;

FIG. 4 is an enlarged view of a portion of the structure shown in FIG.3;

FIG. 5 is an enlarged partial cross-sectional view of the cuttingapparatus shown in FIG. 1;

FIG. 6 is a cross-sectional view taken along lines 6-6 of FIG. 5;

FIG. 7 is a bottom view of the cutting apparatus shown in FIG. 5;

FIG. 8 is a cross-sectional view of a modified embodiment of the cuttingapparatus shown in FIG. 5;

FIG. 9 is a cross-sectional view taken along lines 99 of FIG. 8;

FIG. 10 is a bottom view of the cutting apparatus shown in FIG. 8;

FIG. 11 is a cross-sectional view of a feeding mechanism for the cuttingapparatus of FIGS. 1-10;

FIG. 12 is a cross-sectional view taken along lines 12-12 of FIG. 11;

FIG. 13 is a cross-sectional view showing the shape of one type ofcutter used in the cutting apparatus of the present invention;

FIG. 14 is a cross-sectional view showing the shape of another type ofcutter used in the cutting apparatus of the present invention;

FIG. 15 is a cross-sectional view showing the shape of a third type ofcutter used in the cutting apparatus of the present invention;

FIG. 16 is a cross-sectional view showing the shape of the grooves whichare cut in the workpiece by the cutters of FIGS. 13-15;

FIG. 17 is a cross-sectional view showing the mounting structure for apair of cutters;

FIG. 18 is a cross-sectional view taken along lines 18-18 of FIG. 17;

FIG. 19 is a cross-sectional view, on an enlarged scale, showing oneorientation of the cutter in the mounting structure therefor;

FIG. 20 is a cross-sectional view, on an enlarged scale, showing analternative orientation of the cutter in the mounting structuretherefor;

FIG. 21 is a side elevation of another embodiment of the cuttingapparatus of the present invention;

FIG. 22 is a cross-sectional view of the cutting apparatus shown in FIG.21;

FIG. 23 is a plan view of the cutting apparatus shown in FIG. 22;

FIG. 24 is a cross-sectional view of still another embodiment of thecutting apparatus of the present invention;

FIG. 25 is an enlarged view of one of the hydraulic actuator mechanismsshown in FIG. 24; and

FIG. 26 is an enlarged view of another hydraulic actuator mechanismshown in FIG. 24.

which the cutting means generally designated at 2 is supported. Theframework is mounted on a base 3 having support means generallyindicated at 4 for supporting a workpiece 5. As shown in FIG. 1, thecutting 0 means overlies the workpiece. A cam-cam follower mechanism 6is provided for controlling the movement of the cutting means relativeto the workpiece. As more fully described below, there are threeseparate cutting units 2' forming the cutting means. For clarity,however, only one unit is shown in FIG. 1.

In FIG.. 2, the workpiece is shown with the seal grooves formed therein.With the preferred embodiment of the invention, the cutting apparatus isconstructed to cut the side seal grooves in the side faces of the rotorof a Wankel engine. Each side of the rotor is to include three pairs ofseal grooves 7, 7', 8, 8", and 2 Each pair of seal grooves runs along apath adjacent one of the edges 7, 8" and 9" of the rotor. The sealgrooves 7, 8 and 9, and similarly the grooves 7 8 and 9', intersect attheir ends adjacent the apexes of the rotor in small zones ofintersection designated 10, 11 and 12. In construction, these zones arecavities formed in each side face of the rotor to a depth at least equalto the depth of the seal grooves to be cut. At the apexes of the rotor,slots 10', 11' and 12 are formed for receiving the apex seals of therotor.

As shown in FIG. 2, each of the side seal grooves follows an arcuatepath related to the arcuate shape of the adjacent edge of the rotor.More particularly, the grooves 7, 7' and the edge 7" of the rotor have acommon center of curvature 13. Similarly, the grooves 8,

8" and the rotor edge? have a common center of curvature 14 while thegrooves 9, 9' and the rotor edge 9" have a common center of curvature15.

For cutting the grooves along the arcuate paths shown in FIG. 2, thecam-cam follower mechanism 6 is employed. FIG. 3 shows the orientationof the cam-cam follower mechanism relative to the rotor workpiece 5. Thecam-cam follower mechanism includes a cam member 16 and three followerunits 17, 18 and 19 disposed at from each other about a common point 20.One of the units 17 is shown in FIG. 1; and from FIG. 2 it will be notedthat the point 20 defines the center of the segment of the workpiecebounded by the grooves. FIG. 4 is an enlarged view of the lower portionof the cam-cam follower and workpiece as shown in FIG. 3 depicting themovement of one cam follower unit 17 about an apex of the cam and thecorresponding movement of one of the cutting units about one of theapexes of the rotor.

In construction, the cam member is annular in shape and provided witharcuately shaped cam tracking means in the form of two inner elongatedtracking surfaces 21, 22 and a single outerelongated tracking surface23. Each of the cam follower units includes three bearing means in theform of rollers 24, 25, and 26 engaging, respectively, against the twoinner and outer tracking surfaces 21, 22, 23 of the cam member. The twoinner tracking surfaces are disposed at different levels relative totheir lengths. With references to FIGS. 3 and 4, the inner trackingsurface 21 is disposed below the surface 22 as measured in a directionperpendicular to the plane of the paper on which these figures appear.Similarly, the rollers 24 and 25 of the follower units which ride alongthe inner tracking surfaces are disposed at different levels. In theconstruction shown in FIGS. 2 and 3, the leading roller 24 is lower thanthe roller 25 so that roller 24- rolls along surface 211 and roller 25along surface 22.

The roller 26 of each of the follower units rides along the single outertracking surface of the cam member and holds the follower units with therollers 2d and 25 properly riding on the tracking surfaces of the cam.Advantageously, theouter roller 26 is biased into engagement with theouter tracking surface of the cam as more fully described below.

The tracking surfaces of the cam member are divided into three sections,one corresponding to each pair of curved grooves to be formed in therotor. The sections are identical in construction since the three pairsof grooves are identical in shape. Also, the three sections of thetracking surfaces are directly related to the three pairs of grooves tobe cut in therotor. In particular, the section of the tracking surfaces211,22, 23 which is used for cutting the grooves 7, 7' is formed with'acenter of curvature 13 which is the same as that of the grooves 7, 7.Similarly, the sections of the other tracking surfaces used for cuttingthe grooves 8, 8' and 9, 9' are formed with centers of curvature at 14and 115, respectively.

The arcuate length of each of the sections .of the tracking surfaces 21,22, 23 is dependent on the construction of the follower units. With thepresent invention, each follower unit is constructed with a cutting unit2' mounted radially inwardly of the cam member and in a plane P-Pextending centrally between the rollers 24 and 25 and through the centerof the roller 26..Ihe construction of the follower units with the threerollers oriented in this way maintain the plane P--P at all time normalto the grooves being cut.

With the follower construction of the present invention and the followerunits moving about the cam member in a counterclockwise direction, theroller 2% leads the roller 25. This, in turn, requires that the trackingsurfaces 21 and 22 adjacent the apexes of the cam member be speciallycontoured. For example, with reference to the section of the trackingsurfaces followed for cutting the grooves 7, 7', the tracking surface 22will extend along its arcuate path (with a center of curvature at 13)past the point at which the plane P--P intersects this surface when thecutting unit is at the end of its cutting stroke in the grooves 7, 7 Theposition of the roller 24 on tracking surface 2i when the cutter unitfinishes this cutting stroke is shown by dashed lines in FIG. 4.Similarly, the tracking surface 22 will extend along its arcuate path(with a center of curvature i3) to a location short of the point atwhichthe plane P-P intersects this surface when the cutting unit is locatedat the ends of the grooves 7, 7'. The position of the roller 25 on thetracking surface 22 at the time when the cutting unit is located at theend of this cutting stroke is shown by dashed lines in FIG. 4.

As the cam follower unit continues its counterclockwise movement aboutthe earn from the position shown by the dashed lines of the rollers 24,25, 26 to the position of the rollers shown in dotted lines where theplane P -I andthe cutting unitgre aligned with the begin; ning of thegrooves 8, 8', it is necessary that the cutter unit remain located inthe zone 10. As indicated above,

this zone is a cavity formed in the workpiece and is thus void ofworkpiece material. Accordingly, turning of the cutters is readilyeffected.

To turn the follower unit about the cutter unit when located in the zone10, the inner tracking surfaces of the cam member and undercut as shownin FIGS. 3 and 4i. The centers of curvature of these undercut sectionsof the tracking surfaces 21 and 22 are located in the zoneltL'Similarly, the section of the outer tracking surface 23 between thepoint at which the plane P-P extends through the ends of the grooves 7,7" and the point at which this plane extends through the adjacent endsof the grooves d, 8 is formed with instantaneous centers of curvaturelocated in the zone 10.With the preferred construction, the centers ofcurvature of these sections move through the zone 10 since the cutterunit will have a slight linear movement through the zone during theturning operation.

The undercut segments of the tracking surfaces 21, 22 and thecorresponding segment of the tracking surface 23 define turning sectionsand function to turn each of the follower units about the apexes of thecam member. With this turning movement, the cutting units are moved fromthe end of one pair of grooves to the beginning of the next pair ofgrooves while held within the connecting zone of intersection. With therotor construction. having the zones of intersection formed by cavities,the turning of the cutting units may be readily effected with continuousmovement of the follower units relative to the cam member. Thus, thedrive for the follower units can be a continuously operating constantspeed device.

The particular size of the cam member relative to the grooves to be cutin the rotor is determined, in part, by the speed in which the followerunit is to rotate about the apexes of the rotor. The size of thecam andthe rel ative size of the rollers is also determined by the cam geometryrequired for effecting proper running of the rollers on the trackingsurfaces. With the cam constructions of the present invention, the sizeof the cam is related to the size of the rotor and the grooves to be cutso that an efficient cutting operation is obtained.

FIGS. 5, t6 and 7 show one construction-of applicant's cutting apparatuswherein the relative movement of the cam follower units and cam memberare effected by power driving each of the follower unit rollers 26 alongthe outer tracking surface of the cam member. A stationary post 2'7 isvertically mounted with its axis at right angles to the rotor workpieceand extending through the point 20. Follower support means in the formof a housing 28 is rotatably mounted on the post 27 by way of bearings27'. The housing has three extensions 29, 30, M as shown in FIG. 7extending radially from the axis of the post 27 and spacedat 120 fromeach other. Each of these extensions is adapted to receive one of thefollower units I7, 18 and 19.

In construction, each follower unit includes a slide 32 mounted in oneof the extensions of the follower support means for radial slidingmovement along the extension. As shown in FIG. 6 each extension isprovided with a slide way 29' and associated bearings 29" for slidablymounting the slide 32. A post 33 depends fromthe slide member 32 androtatably supports a housing 3d. The housing 34 carries the followerrollers 24 and 25 for rotation about axes extending parallel to the axesof rotation of the posts 27 and 33. Also, the housing supports ahydraulic drive motor 35 having an output shaft 35' on which the roller26 of the follower unit is secured.

The hydraulic drive motor for the roller 26 is mounted in an eccentric36 by way of a mounting ring 37. The eccentric is biased in a directionthat urges the roller 26 against the outer tracking surface of the cam.In particular, as shown in FIG. 7, a lever 38 is attached to theeccentric and extends outwardly therefrom. The end of the lever isloosely fitted over a screw 39 which is, in turn, threadedly engaged ina bracket 40 on the housing 34. A spherical washer 41 and a series ofspring washers 42 acting between a collar 43 on the screw 39 and thelever 38 urges the eccentric counterclockwise (as viewed in FIG. 7) toload the roller 26 against the outer tracking surface of the cam member.

The roller 26 of each of the roller units, by being power driven, causesthe follower support means to rotate about the post 27 and point 20. Byhaving each of the follower units slidably and rotatably mounted asdescribed above, they may properly move in arcuate paths having centersof rotation common to those of the grooves to be cut in the rotorworkpiece. Although the grooves cut in the rotor described above areformed with the centers of curvature common to the centers of curvatureof the edges of the rotor, this is not necessary. For example, thegrooves could be formed with a smaller curvature than that of the edgesof the rotor. The cam would be shaped accordingly.

In FIGS. 8, 9 and another embodiment of the cutting apparatus is shown.In this embodiment, the basic I relation between the cam and camfollower means and between the workpiece and the cutting means is thesame as shown in FIGS. 5, 6 and 7. That is, the workpiece and cam areheld stationary while the cam follower and cutting means move about thecam. The primary difference in the constructions shown in FIGS. 8, 9 andIt) relates to the drive for the cam follower units.

A center post 44 is mounted with its longitudinal axis extending throughthe point 20. The post is rotatably mounted within a housing 45 by wayof bearings 46. The post 44 is driven in rotation at a constant speed bya motor 47 through pulleys 48, 49 and a drive belt 50; the motor 47being fixed to the housing 45. A three arm structure 51 is secured tothe post 44 at its lower end.

The structure 51 includes three extensions 52, 53, 54 spaced at l fromeach other. A shaft 55 is rotatably secured to each of the extensionsand extends downwardly therefrom. Secured to each shaft 55 at its lowerend is a slide guide 56 on which a housing 57 is'slidably mounted. Asshown in FIG; 9, roller guides 58 are attached to the housing 57 forholding rollers 59 engaging the slide guide 56.

The rollers 24 and which contact the lower and upper inner trackingsurfaces 21, 22 of the cam are mounted on the housing 57.

A slide 60 is held within the housing 57 by a plate 61. This slide 60holds the follower roller 26 contacting the outer tracking surfaces ofthe cam 16. The slide 60 is biased toward the center of the apparatus bymeans of spring washers 62; and thus the roller 26 is held pressedagainst the cam. An adjusting screw 63 is provided for adjusting thepressure with which the roller 26 is urged against the cam. Thisadjusting screw is threadedly mounted in the housing 57. A cutting unit2' is supported on each housing 57 laterally inwardly of the cam and inoverlying relation with the rotor workpiece 5.

The movement of each cam follower unit about the cam is the same as withthe embodiment shown in FIGS. 5, 6, and 7. The sliding, rotativemounting of the follower units permits them to adjust and move about thecam while maintaining the cutters at all times normal to the groovesbeing cut.

In FIGS. 8, 9 and 10, it will be noted that the cam 16 is held in itsfixed position by cam support means 64 extending downwardly from thehousing 45. If desired, the cam could instead be supported from below aswith the embodiment of FIGS. 5, 6, and 7. In the latter case, an openingin the support would be provided for permitting placement and removal ofsuccessive workpieces.

In each embodiment described above, it is necessary that the workpiecebe fed up into the cutting means or that the cutting means be feddownwardly into the workpiece. In accordance with the teachings of thepresent invention, this relative movement of the cutting means andworkpiece is affected during the time at which the cutter units arelocated in the zones of inter sections 10, 11 and 12 on the rotor. I

FIGS. 11 and 12 show a feeding mechanism for moving the workpieceupwardly into the cutting means. In providing this feed, it is necessarythat provision be made for initially feeding the workpiece toward thecutting means at a fast speed to place it properly before starting thecutting operation. This fast speed is also necessary for lowering theworkpiece from the cutting means after the cutting operation has beencompleted. In accordance with the teachings of the present invention,the workpiece is also fed into the cutter units at a slow speed duringthe cutting operation. This movement is through a successive number ofsmall increments equal to a fraction of the total depth of the cut to bemade and is accomplished when the cutter units are located at the zonesof intersection of the grooves.

As shown in FIG. 11, a motor 65 is mounted on the base 3 of the cuttingapparatus. A coupling 66 connects the shaft 65 of the motor to a shaft67. The shaft 67 is supported by ball bearings 68 for rotation on thebase 3. Shaft 67 is selectively connected to a secondary shaft 69through one of two clutch means 70 and 71. The shaft 69 is, in turn,provided with a worm 72 engaging a worm wheel 73 mounted on a shaft 74to which the workpiece support means 75 is fixed.

Depending on which clutch 70 or 71 is engaged, the feed of the workpiecesupport 75 will be at a fast or slow speed. More particularly, the shaft67 is connected to the shaft 69 through two drive paths. First, shaft 67has a gear 76 which meshes with a gear 77 on a support shaft 78.Secondary shaft 69 is rotatably mounted in shaft 78 by means of a needlebearing 79. The clutch 70 is an electromagnetic clutch of conventionalconstruction which when energized will drivingly connect the supportshaft 78 to the secondary shaft 69. When this clutch is energized, theshaft 69 will rotate at the same speed as the shaft 67.

Shaft 74 is threadedly received in a nut 80 and extends rotatablythrough two sleeve members 81 and 82. Sleeve member 81 provides asupport for the nut 80 which is held thereon by a clamp 83. Sleevemember 82, on the other hand, is rotatably mounted on the base structure3 by means of bosses 84 and roller bearing 85. More particularly, thelower end of the sleeve member 82 includes a flange 86 rotatably mountedbetween the bosses 84 by way of the bearings 85. The two sleeves 81 and82 also hold the worm wheel 73 clamped thereon. Thus, rotation of theworm wheel 73 will, in turn, effect rotation of the nut 89. The shaft 74is fixed to the workpiece support 75 at both its upper and lower ends.To provide the connection at the lower end of the shaft, the support 75has frame structure extending downwardly the length of the shaft withlower arm sections extending radially inwardly. A key and lock nut 87holds these arm sections on the shaft.

When the worm wheel 73 is caused to rotate, the nut 80 will rotate andthus move the shaft 74 vertically through the nut. This will carry theworkpiece support 75 up or down on the base 3. To facilitate thismovement, the downwardly extending portions of the support 75 isprovided with ball guides 68 operatively associated with similar guides89 on the base 3. Suitable bearings 90 are positioned between theguides.

The feed as described above effects a fast movement of the workpiece toand from the cutting means. For effecting a slow incrementalmovement ofthe workpiece during the cutting operation, the electromagnetic clutch71 is energized while the clutch 79 is deenergized. Clutch 71 connectsthe shaft 67 to the shaft 69 through a pair of worm mechanisms. As shownin FIG. 11, the shaft 67 is provided with a worm 91 while the shaft 69is provided with a worm wheel 92. A cross shaft 93 is rotatably mountedon the base overlying the shaft 67 and 69 by way of the mountingsurfaces 941.

Cross shaft 93 includes aworm wheel 95 and worm 96.

The worm wheel 95 cooperates with the worm 91 of the shaft 67 while theworm 96 cooperates with the worm wheel 92 of the shaft 69. When theclutch '71 is energized, the speed of rotation of the shaft 69 isreduced by the double worm reduction connecting the drive shaft 67.This, in turn, effects a very slow feeding movement of the workpiecetoward the cutting means.

In accordance with the teachings of the present invention, each of threecutting units 1'7, 16 and 19 includes a pair of single point cutters forcutting the grooves of each pair at the same time. In constructions, theshape of the cutters of each unit differs. In FIGS. 13, 14 and 15, thecutters of each unit are shown at 97, 98, 99. FIG. 16 shows the overallshape of the groove v 7 being cut on the workpiece. This shape of thefinal groove is shown in 15.

The shape of the cuttersand their orientation relative to the workpieceis such as to produce an efficient cutting with each cutter assistingthe other cutters. In particular, the first cutter 96 has a cuttingwidth W-il which is less than the cutting width W-2 of the second cutter98 and less than the cutting width 61-3 of the third cutter 99. Also,the cutter 97 is enlargedabove the cutting edge to provide strength.Relative to the workpiece being cut, the three cutters are disposed atdifferent levels. More particularly, the cutter 9'? is disposed at alevel closer to the workpiece than the cutter 98 while the cutter 98 isdisposed closer to the workpiece than the cutter 99. To effect thisorientation of phantom lines in FIGS. 13, 16 and the three cutters theyare mounted by way of cutter holders 100 on the cam followers atdifferent heights above the workpiece.

FIGS. 17 and 18 show the holder construction for supporting the cutters97. The holder includes a bore 101 in which the cutters are disposedwith the cutting edges extending downwardly out of the holder. Thecutters are held in spaced relation within the bore by means of blockmembers 192, 103, 104 and 105. Set

screws 106 and 1117 are threadedly supported within the holder andpressed against the blocks 104 and 105. The vertical position of thecutters within the holder can be readily set prior to tightening of theset screws. The cutter holder 101) is itself held within a retainer 199by means of set screws one of which is shown at 199. The retainer isattached to the cam follower by bolts extending through the apertures119. A- key 111 is provided for holding the cutter holder in properangular relationship in the retainer 198. As shown in FIG. 19, thecutter may have its cutting edge on the center line of the retainer1116. Alternatively, the cutter may be located offset from the centerline of the retainer as shown in FIG. 20.

In performing a cutting operation, the cutters are moved successivelyalong arcuate pathsto cut the grooves 7, 7 9, 9', and 9, 9'. The groovesare not cut to their final depth in one cutting stroke. Instead, thecutters are moved downwardly into the workpiece by small increments at atime. This downward incremental movement of the cutters is effectedwhile they are disposed within the zones of intersection 10, 11 and 12and while the cutters are turning, free of the workpiece material.Suitable means is provided for effecting this incremental feeding. Withreference to FIGS. 112 where the apparatus is constructed for moving theworkpiece upwardly into the cutters. The feeding cycle may beautomatically initiated by suitable means such as a limit switch 112shown diagrammatically in FIGS. 3, 7 and 16. This limit switch islocated in the path of movement of the follower unit structure with acontact 113 adapted to cooperate with a contact 1141 on one of thefollower unit structures. Closing of these contacts momentarily closesan electrical circuit to intermittently actuate the electromagneticclutch 71 each time the-follower units make a complete revolution aboutthe cam member.

in the presently preferred construction of the invention, the firstcutter 97 is disposed at a level below the second cutter equal to theincrement through which all the cutters are moved when in the zones ofintersection between the grooves being cut. Similarly, the second cutteris located at a level below the third cutter which is equal to this sameincrement of movement. With this construction, the cutting operation ofthe grooves will be performed by first moving the workpiece upwardlytoward the cutting units at a fast speed. From this starting position,the workpiece will then be'moved at a slower speed through one incrementwhile the'cutter units are disposed in alignment with the three zones ofintersection between the grooves to be cut. This feedling will move thefirst cutters 97 of thefirst cutting unit down below the upper-surfaceof the workpiece while the cutters 99 and 99 of the second and thirdunits will remain spaced above the workpiece. The cutters will then bemoved through one complete revolution so that the cutters 97 make aninitial cut along the moved through still another increment to move thethird cutters 99 below the upper surface of the workpiece. Upon rotationof the cutters through one more revolution, all three units will beperforming a cutting operation. Each time the cutters revolve a completerevolution and align themselves within the zones of intersection of thecutting paths, the workpiece will be moved an additional increment intothe cutters. This cutting procedure will continue until each groove iscut to its final depth.

With the preferred cutting arrangement of the present invention, thefirst cutter will perform a rough cutting, the second cutter willperform a semi-finishing operation and the third cutter will finish thegroove to the desired surface finish. In accordance with the teachingsof the present invention, the cutters assist each other in performingthe cutting operation. More particularly, once all of the cutters areperforming a cutting operation, the cut performed by the third cutters99 will provide clearance for chips removed from the workpiece by thesecond cutters 98; and similarly, the second cutters 98 will provideclearance for the chips beingremoved by the first cutters 97.

Instead of using three different types of cutters as described above,however, the three pairs of cutters may all be used to finish thegrooves. In this case, the feeding of the workpiece relative to thecutters will be effected each time the cutting units reach the next zoneof intersection. Thus, for each complete revolution of the cutters aboutthe workpiece, the cutters will be fed into the workpiece three times.For automatic control of this feeding, a limit switch 112 is located ateach apex of the cam for engagement by the contact 114 on the followerunit 17.

When cutting the seal grooves in the rotor for a Wankel engine, theoverall width of the groove may, for example, be approximately 0.040inch. The first cutter which performs the rough cutting will have acutting width of approximately 0.025 inch and an upper enlarged sectionof about 0.036 inch. This will leave a clearance of about 0.002 oneither side of these cutters 97 and the walls of the groove being cut.The second cutter may have a uniform cross-sectional width ofapproximately 0.032 inch to leave a clearance of 0.004 inch at eitherside of the groove. Finally, the third cutter will have a width equal tothe final width of the groove. With incremental movements of theworkpiece toward the cutters of 0.003 inch it will take approximately 60revolutions to cut a groove having-a total depth of 0.170 inch. In anycase where the total depth is not an exact multiple of the incrementalmovement of the cutters into the workpiece, this may be compensated forby the initial location to which the workpiece is moved at the startingof the cutting operation. Also, the final incremental feeding can beadjusted.

After the cutting operation has been completed on both sides of therotor, it is ready to receive the seal strips without furtherprocessing. The grooves will be accurately formed to properly receivethese strips and the counter-sunk bottom of the groove will providespace for spring means on which the seal strips are to be supported.

FIGS. 21, 22 and 23 shows an alternative embodiment of the presentinvention in which the cutter units are supported on stationary postsand both the cam and workpiece are rotated to effect movement of the camfollowers with respect to the cam and the cutter units with respect tothe workpiece. For clarity, only one follower unit and cutting unit isshown in FIGS. 21 and 22. As shown in FIG. 23, however, three unitsspaced at 120 are provided. 1

Referring to FIGS. 21 and 22, the workpiece 5 is mounted on a platformwhich is, in turn, rotatably supported by bearings 116 on a slide member117. The slide member 117 includes ball guides 1 18 disposed oppositeball guides 119 fixed to the base structure 3 of the apparatus. Suitableballs 120 are disposed between the two ball guides to permit slidingmovement of the slide member 117 relative to the base in a verticaldirection.

A hydraulic motor 121 is mounted on the slide member 117 and has itsoutput shaft 122 connected to an adaptor member 123 and coupling 124.The coupling supports a sprocket gear 125. The sprocket gear 125,through a sprocket chain 126, rotates a sprocket gear 127, in turn,fixed to a support shaft 128 by way of a spline member 128 The driveconnection between the motor 121 and the shaft 128, as provided by thesprocket and chain connection, effects continuous r0- tation of theshaft. The upper end of the shaft 128 is connected via a clutch 129 tothe support platform 115; With the clutch 129 energized, continuousrotation of the shaft 128 effects continuous rotation of the supportplatform and the workpiece 5 relative to the overlying cutting units.

In this embodiment of the invention, it is necessary that the cam 16 berotated in unison with the workpiece. For this purpose, the cam isrotatably supported on the base structure 3 of the machine via thebearings 130 and support structure 131. Vertically extending posts 132couple the cam support structure to the workpiece support platform 115.Accordingly, rotation of the platform will, through the connectionprovided by the posts 132 produce simultaneous rotation of the camrelative to the cam follower units.

With the embodiment of the invention shown in FIGS. 21, 22 and 23,separate drive connections are provided for feeding the workpiece towardthe cutter units, one for fast feeding of the workpiece prior to andafter the cutting cycle and one for slow feeding the workpiece in smallincrements during the cutting cycle. As shown in FIG. 22, the outputshaft 122 is connected to one side of an electromagnetic clutch 133 byway of the adaptor member 123 and coupling 124. The adaptor memberrotatably supports a shaft 134 by way of a needle bearing 135. The otherside of the electromagnetic clutch 133 is mounted on the shafl 134 so asto permit selective coupling of the drive motor 121 to the shaft 134.The coupling and adaptor member are themselves rotatably supported onthe slide member 117 by way of bearings 135.

The upper end of the shaft 134 is provided with a gear 136 meshing witha gear 137 fixed to a nut member 138. The nut member is rotatablymounted on the base structure 3 and held against vertical movementrelative to the slide 117 by means of a clamping structure 139 andbearing means 140. The support shaft 128 extends in threaded engagementthrough the nut member and is adapted to be moved vertically in an upand down direction in response to rotation of the nut member. As seen inFIG. 22, the threaded support shaft is rotatably supported at its lowerend in the slide member 117 by means of a bearing 141.

1. A cutting apparatus for cutting a surface of a workpiece along atleast two predetermined paths intersecting each other at an acute anglein a small zone comprising: a. support means for supporting saidworkpiece; b. a cam member; c. a follower movable relatively along saidcam; d. cutting means mounted on said follower for movement therewith;e. driving means for moving said follower relatively along said cammember, said cam member and follower having cooperating means foreffecting movement of the cutting means along said predetermined pathsas said follower moves relatively along said cam member; and f. controlmeans for turning said follower on said cam member to move said cuttingmeans from the end of one of said paths to the beginning of the otherwhile holding said cutting means in the zone of intersection of said twopaths.
 2. a threaded shaft connected to the platform and extendingdownwardly therefrom; and b. the feeding means includes:
 2. a firstpower actuator for moving the slide means through a predetermineddistance to move the workpiece to and from a starting position relativeto the cutting units,
 2. an outer elongated tracking surface;
 2. saidtracking surfaces including first, second and third sections directlyrelated to the first, second and third paths to be cut on the workpiece,and
 2. a housing rotatably supported on said post for rotation aboutsaid longitudinal axis,
 2. a third bearing means engaging the outertracking surface,
 2. A cutting apparatus according to claim 1 wherein:a. said two predetermined paths are arcuate paths with the concave sidesthereof facing eath other; b. said cam member has a first arcuatelyshaped means directly related to said first path and a second arcuatelyshaped means directly related to said second path; c. said followerincludes a bearing means engaging said first and second arcuately shapedmeans as said follower moves relatively along said cam member; d. saidcutter means is mounted on said follower facing the concave side of saidarcuately shaped means as the follower moves along the cam member; ande. said first and second arcuately shaped means and said bearing meansdefine said cooperating means for effecting movemEnt of said cuttingmeans along said predetermined paths.
 2. a housing for rotatablysupporting said post,
 3. three radially directed extensions fixed tosaid post,
 3. said first and second bearing means being spaced equallyfrom each other on opposite sides of a plane extending therebetween andthrough the third bearing means; and c. the first, second and thirdsections of the tracking surfaces and the bearing means define thecooperating means effecting movement of said cutting means along saidpredetermined paths.
 3. said tracking surfaces each having first, secondand third sections directly related to the first, second and third pathsto be cut on said workpiece, and
 3. three radially directed extensionsfixed to said housing,
 3. A cutting apparatus according to claim 2wherein: a. said first arcuate path and said first arcuately shapedmeans describe portions of circles with a common center of curvature; b.said second arcuate path and said second arcuately shaped means describeportions of circles with a common center of curvature; and c. saidcontrol means for turning the follower on the cam member includes thirdarcuately shaped means connecting said first and second arcuately shapedmeans together and having instantaneous centers of curvature within saidzone of intersection of the two paths being cut on said workpiece. 3.said tracking surfaces further including turning sections connecting thefirst, second and third sections and defining said control means; b.said follower means includes bearing means for engaging the inner andouter tracking surfaces for movement along the lengths thereof; and c.the first, second, and third sections of the tracking surfaces and thebearing means define the cooperating means effecting movement of saidcutting means along said predetermined paths.
 3. a nut member threadedlyengaging said threaded shaft and fixed to the slide means againstrotation,
 4. a second power actuator mounted on the slide means andhaving a pawl connected thereto,
 4. A cutting apparatus for cutting asurface of a workpiece along first, second and third predetermined pathsintersecting each other at their ends in small zones comprising: a.support means for supporting said workpiece; b. a cam member having anannular shape disposed in surrounding relation to said workpiece; c.follower means mounted for relative movement along said cam; d. cuttingmeans mounted on said follower means for movement therewith; e. drivingmeans for moving said follower means relatively along said cam member,said cam member and follower means having cooperating means foreffecting movement of the cutting means along said predetermined pathsas said follower means moves relatively along said cam member; and f.control means for turning said follower means on said cam member to movesaid cutting means from the end of each one of said paths to thebeginning of the next adjacent path while holding said cutting means inthe zone of intersection of these two paths.
 4. slide means mounted oneach of said extensions for sliding linear movement toward and away fromthe axis of rotation of said housing, and
 4. said tracking surfacesfurther having turning sections connecting the first, second and thirdsections and defining said control means; b. said follower meansincludes:
 4. a slide support rotatably mounted on each of saidextensions for rotation about an axis extending parallel to the axis ofrotation of said support post, and
 5. a first gear fixed to the threadedshaft and operatively engaged by said pawl to effect incrementalrotation of the shaft in one direction and raising of said platform uponincremental linear movement of the pawl,
 5. means for rotatably mountinga follower unit on each of said slide means for rotation about an axisextending parallel to the axis of rotation of said housing; and b. saiddriving means includes a drive motor mounted on each of said followerunit and having an output shaft on which the third roller of thefollower unit is mounted.
 5. A cutting apparatus according to claim 4wherein: a. said cam member includes:
 5. slide means for mounting afollower unit on each of said side supports for sliding linear movementtoward and away from the point about which the support post rotates; andb. said driving means includes a drive motor supported on said housingfor power rotating said post.
 6. A cutting apparatus according to claim5 wherein: a. said driving means includes means for continuously movingsaid follower means in one direction relatively along said cam member tomove said cutting means successively through said first, second andthird predetermined paths.
 6. a third power actuator mounted on theslide means and having a rack member fixed thereto, and
 7. a second gearfixed to the threaded shaft and operatively associated with the rack forrotating the shaft continuously in a direction opposite to the rotationeffected by the activation of the second power actuator to lower theplatform to its starting position.
 7. A cutting apparatus according toclaim 4 wherein: a. said cam member includes:
 8. A cutting apparatusaccording to claim 7 wherein: a. said follower means comprises first,second and third follower units, each having said first, second andthird bearing means, said units being spaced about a predetermined pointat 120* with respect to each other for simultaneously engaging thefirst, second and third sections of the tracking surfaces.
 9. A cuttingapparatus according to claim 8 wherein: a. each of said bearing meanscomprises a rotatable roller for rolling against said tracking surfaces.10. A cutting apparatus according to claim 9 further including: a.follower support means for said follower units mounted for rotationabout said predetermined point; and b. means for mounting each of saidfollower units on said follower support means for both rotation aboutand linear sliding movement toward and away from said predeterminedpoint.
 11. A cutting apparatus according to claim 10 wherein: a. saiddriving means includes power means for rotating each of said thirdrollers to effect movement of said follower units along the cam member.12. A cutting apparatus according to claim 10 wherein: a. said followersupport means includes:
 13. A cutting apparatus according to claim 10wherein: a. said driving means includes power means directly connectedto said follower support means for rotating same about said point.
 14. Acutting apparatus according to claim 10 wherein: a. said followersupport means includes:
 15. A cutting apparatus according to claim 10wherein: a. said driving means includes power means for rotating thesupport for said workpiece and said cam member simultaneously about saidpredetermined point.
 16. A cutting apparatus according to claim 10further including: a. feeding means for moving said workpiece into saidcutting means along a direction extending at right angles to themovement of the cutting means along said predetermined paths.
 17. Acutting apparatus according to claim 16 wherein: a. said feeding meansincludes control means for effecting incremental movement of theworkpiece when the cutting means are aligned within said zones onintersection.
 18. A cutting apparatus according to claim 10 wherein: a.said cutting means includes a cutting unit mounted on each of saidfollower units in overlying relation with the workpiece, each of saidcutting units being mounted at a different level relative to theworkpiece; b. feeding means for moving said workpiece toward saidcutting units along a direction extending at right angles to themovement of the cutting units along said predetermined paths; c. feedingmeans for effecting inCremental feeding movement of the workpiece towardthe cutting units when the cutting units are aligned with the zones ofintersection of said predetermined paths.
 19. A cutting apparatusaccording to claim 18 wherein: a. the cutting unit mounted at a levelclosest to the workpiece includes cutter means having a cutting widthless than that of the cutters on the other two units; b. the cuttingunit mounted at a level farthest from the workpiece includes cuttermeans having a width greater than that of the cutter means on the othertwo cutting units.
 20. A cutting apparatus according to claim 19wherein: a. the cutter units are spaced from each other at differentlevels relative to the workpiece with the difference between each levelbeing at least equal to the length of incremental movement of theworkpiece.
 21. A cutting apparatus according to claim 19 wherein: a. thesupport means for supporting the workpiece includes:
 22. A cuttingapparatus for cutting a workpiece to a predetermined depth along threepaths which intersect each other at their ends comprising: a. first,second and third cutters mounted for sequential movement through saidthree paths with the first cutter leading the second and the secondleading the third; b. said first cutter having a cutting width less thanthat of the other two cutters and being disposed relative to the othercutters at a level closer to the workpiece; c. said second cutter havinga cutting width less than that of the third cutter and being disposedrelative to the third cutter at a level closer to the workpiece; and d.feeding means for moving said cutters into said workpiece in incrementsuntil the third cutter reaches said predetermined depth.
 23. A cuttingapparatus according to claim 22 wherein: a. the paths along theworkpiece through which the cutters move intersect each other in zonesvoid of workpiece material; and b. said feeding means moves said cuttersinto said workpiece through said increments when the cutters are in saidzones.
 24. A cutting apparatus according to claim 23 further including:a. rotatable support means for supporting said cutter units at equallyspaced intervals about the axis of rotation of the support means; b.drive means for rotating said support means about said axes; and c.turning means for turning said cutter units when in said zones ofintersection to move them from alignment with the end of one path andinto alignment with the beginning of the next path.
 25. A cuttingapparatus according to claim 24 wherein: a. the three cutters are spacedfrom each other at different levels relative to said workpiece with thedistance between each level being at least equal to the length of theincrementaL movement of the cutters.